/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.paging

import androidx.annotation.RestrictTo
import androidx.paging.LoadState.NotLoading
import kotlin.jvm.JvmName

/** Collection of pagination [LoadState]s - refresh, prepend, and append. */
public data class LoadStates(
    /** [LoadState] corresponding to [LoadType.REFRESH] loads. */
    public val refresh: LoadState,
    /** [LoadState] corresponding to [LoadType.PREPEND] loads. */
    public val prepend: LoadState,
    /** [LoadState] corresponding to [LoadType.APPEND] loads. */
    public val append: LoadState
) {
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public inline fun forEach(op: (LoadType, LoadState) -> Unit) {
        op(LoadType.REFRESH, refresh)
        op(LoadType.PREPEND, prepend)
        op(LoadType.APPEND, append)
    }

    internal fun modifyState(loadType: LoadType, newState: LoadState): LoadStates {
        return when (loadType) {
            LoadType.APPEND -> copy(append = newState)
            LoadType.PREPEND -> copy(prepend = newState)
            LoadType.REFRESH -> copy(refresh = newState)
        }
    }

    internal fun get(loadType: LoadType) =
        when (loadType) {
            LoadType.REFRESH -> refresh
            LoadType.APPEND -> append
            LoadType.PREPEND -> prepend
        }

    /** Returns true if either one of [refresh], [append], or [prepend] is in [Error] state. */
    @get:JvmName("hasError")
    public val hasError =
        refresh is LoadState.Error || append is LoadState.Error || prepend is LoadState.Error

    /**
     * Returns true if all three LoadState [refresh], [append], and [prepend] are in [NotLoading]
     * state.
     */
    public val isIdle = refresh is NotLoading && append is NotLoading && prepend is NotLoading

    internal companion object {
        val IDLE =
            LoadStates(
                refresh = NotLoading.Incomplete,
                prepend = NotLoading.Incomplete,
                append = NotLoading.Incomplete
            )
    }
}
